dog.cpp

vc源代码

/*
    dog.cpp -- A program demonstrating function pointers.
 */
#include    <stdio.h>
#include    <iostream.h>
#include    <string.h>

const char *Commands[] =
    {
    "come", "done", "fetch", "heel",
    "sit", "speak", "stay"
    };
#define COMMANDS    (sizeof (Commands) / sizeof (char *))

// Declare our functions
void Come(), Done(), Fetch(), Heel();
void Sit(), Speak(), Stay();

// Put the functions in an array of functions
void (*Command[])(void) =
    {Come, Done, Fetch, Heel, Sit, Speak, Stay};

// Binary search function
int Binary (char *In);

int main ()
{
int Action = 0;
int Done;

    Done = Binary ("done");
    if (Done < 0)
    {
        cerr << "Cannot find exit command" << endl;
        return (-1);
    }
//
// Make sure the function table isn't too small. Jumping
// to an undefined spot can be dangerous.
    if (COMMANDS > (sizeof(Command)/sizeof(void(*)(void))))
    {
       cerr << "Function table is too short" << endl;
       return (-1);
    }
    do
    {
        char In[128];
        cout << "Please enter a command: ";
        cin >> In;
        Action = Binary (In);
        if (Action < 0)
        {
            cout << "Valid commands are" << endl;
            for (int x = 0; x < COMMANDS; ++x)
                cout << '\t' << Commands[x] << endl;
            continue;
        }
        Command[Action]();
    } while (Action != Done);
    return (0);
}

int Binary (char *In)
{
int low = 0;
int high = COMMANDS - 1;
int mid, check;

    strlwr (In);
    while (low <= high)
    {
        mid = (low + high) / 2;
        if (!(check = strcmp (In, Commands[mid])))
            return (mid);
        if (check < 0)
            high = mid - 1;
        else
            low = mid + 1;
    }
    return (-1);
}

void Done ()
{
    cout << "Your dog licks your face in enormous ";
    cout << "gratitude" << endl;
}

void Sit()
{
    cout << "Your dog is now sitting" << endl;
}

void Stay()
{
   cout << "Your dog stays put (good dog!)" << endl;
}

void Come()
{
    cout << "Your dog is running toward you" << endl;
}

void Fetch()
{
    cout << "You toss a stick and your dog runs after it";
    cout << endl;
}

void Heel()
{
    cout << "Your dog walking by your side" << endl;
}
void Speak()
{
    cout << "\"Arf!\" says Sandy" << endl;
}